/*
 * Copyright 2002-2014 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.messaging.support;

import java.io.Serializable;
import java.util.Map;

import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;

/**
 * An implementation of {@link Message} with a generic payload.
 * Once created, a GenericMessage is immutable.
 *
 * @author Mark Fisher
 * @see MessageBuilder
 * @since 4.0
 */
public class GenericMessage<T> implements Message<T>, Serializable {

    private static final long serialVersionUID = 4268801052358035098L;


    private final T payload;

    private final MessageHeaders headers;


    /**
     * Create a new message with the given payload.
     *
     * @param payload the message payload (never {@code null})
     */
    public GenericMessage(T payload) {
        this(payload, new MessageHeaders(null));
    }

    /**
     * Create a new message with the given payload and headers.
     * The content of the given header map is copied.
     *
     * @param payload the message payload (never {@code null})
     * @param headers message headers to use for initialization
     */
    public GenericMessage(T payload, Map<String, Object> headers) {
        this(payload, new MessageHeaders(headers));
    }

    /**
     * A constructor with the {@link MessageHeaders} instance to use.
     * <p><strong>Note:</strong> the given {@code MessageHeaders} instance is used
     * directly in the new message, i.e. it is not copied.
     *
     * @param payload the message payload (never {@code null})
     * @param headers message headers
     */
    public GenericMessage(T payload, MessageHeaders headers) {
        Assert.notNull(payload, "Payload must not be null");
        Assert.notNull(headers, "MessageHeaders must not be null");
        this.payload = payload;
        this.headers = headers;
    }


    public T getPayload() {
        return this.payload;
    }

    public MessageHeaders getHeaders() {
        return this.headers;
    }


    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof GenericMessage)) {
            return false;
        }
        GenericMessage<?> otherMsg = (GenericMessage<?>) other;
        // Using nullSafeEquals for proper array equals comparisons
        return (ObjectUtils.nullSafeEquals(this.payload, otherMsg.payload) && this.headers.equals(otherMsg.headers));
    }

    public int hashCode() {
        // Using nullSafeHashCode for proper array hashCode handling
        return (ObjectUtils.nullSafeHashCode(this.payload) * 23 + this.headers.hashCode());
    }

    public String toString() {
        StringBuilder sb = new StringBuilder(getClass().getSimpleName());
        sb.append(" [payload=");
        if (this.payload instanceof byte[]) {
            sb.append("byte[").append(((byte[]) this.payload).length).append("]");
        } else {
            sb.append(this.payload);
        }
        sb.append(", headers=").append(this.headers).append("]");
        return sb.toString();
    }

}
